GREEN BAY – As a coordinator, Mike Pettine has never fielded a defense that finished outside the NFL’s top 10 in yards allowed, and his first season with the Green Bay Packers has a chance to be no different.

The Packers rank a surprising fourth in the NFL with 313.8 yards allowed per game through five weeks. It puts them in a class with top-ranked Jacksonville, second-ranked Chicago and third-ranked Baltimore, three teams whose defensive talent is unquestioned.

Just don’t tell Pettine that fourth-place ranking is all that relevant.

“Top 10,” he said, “in a very poor ranking system.”

Despite having every reason to appreciate yards being the primary indicator evaluating defensive performance, Pettine believes it’s a terrible gauge.

As he noted, the Packers allowing only 264 yards in Detroit didn’t prevent the Lions from dropping 31 points in a win. The Packers couldn’t keep the Lions off the scoreboard because they couldn’t keep them out of the end zone. Detroit scored touchdowns each of the four times it entered the red zone last Sunday.

Two of those drives didn’t accumulate many yards because the Lions started at Green Bay’s 1 and 29 after turnovers.

“There weren’t a lot of yards to give up,” Pettine said.

He believes that’s one example of how yardage can be deceiving. Pettine said he prefers “some type of formula like a quarterback rating” to measure a defense, not simply yards.

The Packers are top five in total defense, but they rank 14th in scoring defense (22.8 points per game) and are tied for 20th in red-zone defense (allowing touchdowns on 62.5 percent of opponents’ trips). Likewise, the Packers are second in pass defense (209 yards allowed per game) but only 12th in opposing passer rating (89.3), a far better indicator of how a team defends the pass.

All those numbers are better than last season under Dom Capers. They’re reason to be optimistic about the defense’s long-term forecast. Pettine said there’s still plenty of improvements to make.

“We’ve got a long way to go,” Pettine said, “till we feel like we’re a truly cohesive unit where guys know what the other guys is doing next to him, and there’s the trust. I think it’s only natural to not have that in the beginning when it’s still a new defense and it’s unfamiliar, till they get comfortable in it and they get a feel for everybody else’s job.

“Usually there’s a tendency to maybe try to do too much. We’re fighting some of that. But I think for the most part you like where we’re headed, but there’s always that urgency to get where you want to go quicker.”

Kicking the yips

Ron Zook acknowledged some kickers would be rattled after missing five kicks in one game, but the Packers special teams coordinator doesn’t expect veteran Mason Crosby to respond that way.

Zook said he spent “probably a lot more time than anybody else” going over the Packers' field-goal operation this week, examining it from all angles. He stressed a successful field goal is snapper, holder and kicker working in unison, along with protection from the offensive line.

Paramount to that process, obviously, is a comfortable and confident kicker. Zook expects to see that in Crosby.

“He’s a pro,” Zook said, “and he’ll fix whatever needs to be fixed. I think he’s probably a little bit more zoned in, if that’s the right word. Mason has always been a pro since I’ve been around him. I’m not one bit worried about him.”

Crosby has recovered from breakdowns before, most notably rebounding from a miserable 2012 season. Zook wasn’t his coach then, but he recalled Crosby inexplicably getting the yips during the annual Family Night practice in training camp last year. Crosby made only 5-of-11 field goals in front of a packed Lambeau Field crowd, missing six of his last seven.

Crosby went on to make 15-of-19 field goals last season, a 78.9 percent clip that ranked only 24th in the NFL. But one of his misses was blocked, and another came after the snap was badly mishandled. The two others were a 59-yard field goal at the end of a half in Green Bay, and a 57-yard kick in windy Pittsburgh.

Otherwise, Crosby was solid through the season.

“He came right back out of that,” Zook said, “and he’ll do the same thing here.”

Injury report

Mike McCarthy wasn’t in the mood to reveal the secrets of his team’s health status Saturday morning, but he suggested right tackle Bryan Bulaga has a decent chance to play Monday night.

Bulaga is questionable against the San Francisco 49ers after being limited in Friday’s padded practice because of a knee injury, McCarthy said.

“I’m not concerned,” the coach said.

McCarthy said backup tackle Jason Spriggs “had a little setback” in Friday’s practice, but did not expound on the severity of his ankle injury. Spriggs, who was questionable on Saturday’s injury report, was carted off the field early in Friday’s practice.

Receivers Randall Cobb (hamstring) and Geronimo Allison (hamstring) appear to be on track to play against the 49ers, but McCarthy wasn’t ready to declare their availability.

“We’ll give them a full week with the extra day Monday,” McCarthy said. “So we’ll see how that goes here today and tomorrow (Sunday).”